I've making a GRP floor for my 3 wheeler project. The area that will be stood on when getting into the car is 300mm x 970mm.

For most of the inner panels I've used 600 gsm woven roving either side of either 300 gsm CSM or 150 gsm where it doesn't need to be as thick.

For the floor, I was thinking of 600 gsm rovings + 450 gsm CSM + 600 gsm rovings + 300 gsm CSM. Will that be enough or should I go thicker still?

For the floor, I'd put a layer of kevlar or somesuch in there....

For the floor I would use a core filler material.

Find some Coremat. Horrible stuff, but does its job.

One layer of 600 either side of 5mm Coremat will do the job well, and be a lot lighter and stiffer than what you proposed.

If you can't find any locally, I've got a roll somewhere. About £4 for the area you need.

Cheers,
Syd.

i would make some ribs - presumably this is same effect as the core mat stuff - it will be stronger for the same wieght or lighter for the same strength.

The glass floor on my Deuce roadster project is very rigid and strong.

It appears to be two diagonally crossed plies of cloth with a layer of the random strand cloth between. There are molded in ribs.